First off AGE makes a big difference in this...in my teens 'love' was so stupid looking back, I'd get so worked up over petty things....in my 20's, it became really clear...you have sex, you have love, you have good people and bad. Depending on your needs/wants any combo is what works.
Most people that have a girlfriend should be playing the field [this is read as anyone younger than mid 20's and ANYONE that has been living on their own for less than 5 years]....a lot of wacky relationships out there that have nothing to go the distance. People like to settle though on relationships, but at the same time will fight tooth and nail over used car pricing, electronics, etc.
In my personal experience, it's usually the guys getting hurt more often, but the girls getting hurt the most. The best or worst story in my book depending how you look at it involves this freshman that was with a chick since middle school...worshipped her. In my opinion at the time, she was growing up faster than him (I had made out/messed around with her one night at a party, and turned further action down because I knew the guy really liked her, I felt really bad about it when he came by late than night to take her home). Anyway, one day he catches her talking to an older guy on campus and they were heavily flirting...pretty much groping each other, he tried to start a fight and got seriously worked. She did run to him and yell at the other guy, but she was totally into it, hands all over the guy...the f'kd up part was about a week later when he snuck in her window like he usually did the other guy was already there and it was not pretty. Details aside, the other guy got the prize, the young guy only got touch action all the years he knew her, but he never tried to go beyond 'making out' really and that was his fault and it's very common. I did it myself when I was really young, but in reality get over she is a princess when you are alone; even the biggest romantic chick wants real action if she is alone with her man.
I thought he was going to kill himself, it was a lot to absorb in person and I am really glad the other guy wasn't a 'rick about it and apoligized and let him leave without getting beat up again...fortunately all it took was a bit of angst and hooking up with a messed up chick (looking back probably cool, but she was some black makeup-clothing / white face powder girl...lightning child as we called them). I heard nothing but stories for the next 3 months until he moved on. Got his man education though We even got him buying his own condoms, although he always did it like 30mins from where we lived.
I have cheated in the past, both directly and what most people's definition of cheating is. I have been cheated on too, in retrospect some of those times she owed me nothing. I have had multiple sexual girlfriends at the same time, to me that is hard to deal with in a way...I like having random partners, but there are a few I am trying to get more serious with; it felt decieving sometimes but at the same time there was no history. If the chick was cool about it, I was scott-free...but if she was asked about where I was last night/etc I would feel bad.
Girlfriend to me is a big gamut, all from someone you just swing by when you don't meet anyone else out to someone you have thoughts of marriage. Now they even have friends with benefits , it's seriously a great thing. No one should base a relationship on intercourse in my opinion. In reality people try so hard to get what's seriously easy to get if you just get out and talk to people.
However, if I am serious about someone and have a need to cheat I will be honest with them. It's all you can do, no use trying to make yourself something you are not. In my opinion, she is better off finding out sooner than later. We all have needs...you don't want to lie to yourself about these...first 5-10 years easy to ignore/get angry sometimes/etc...those next 5-10 years a bit harder, affair here and there....getting abusive (hopefully just verbally), then walking out.
Then there are also relationships that have two people that like their common interests, possibly financial or other interests in common, but have other's they like to have sex with. I am not one of these types of people...but I think that is because I am a bit selfish. If it were open to me to do, I don't know if I'd have a problem with it.
If both parties are ok with something that should be what the rules are though. Cheating is only something you do that you know your 'mate' will hate if they found out you did it behind their back...all else is profit! :beer: